Photo: Reaction Designs A special whistle blown by the boatswain's mates to pass along orders, or pay salute. It's four parts are made of the buoy, the keel, the gun and the shackle. Above, you'll see the piping patterns created. They blew with even pressure, with varying pressure - to give a warbling sound, or they blew evenly and vibrated the tongue which makes a trilling sound. The Bosun/Boatswain modified the sound by opening and closing the hand around the boy, producing